The use of Schottky barrier junctions is well known in the prior art, as well as the utilization of Schottky barrier devices in integrated monolithic circuits. Because of their relatively low forward barrier or turn-on voltage characteristics, they are found attractive for use in integrated circuits for applications such as preventing transistor saturation and to provide faster turn-on time for digital circuits, and faster switching speeds. Because the forward barrier height of these Schottky diodes is inversely proportional to such switching speeds, Schottky barrier diodes with lowered forward barrier heights are desirable.
Copending application Ser. No. 755,272 of J. K. Howard et al., filed Dec. 29, 1976 (assigned to the assignee of this application), describes a method for obtaining stable Schottky barrier diodes by reacting a transition metal barrier contact (e.g. hafnium, zirconium, tantalum, niobium, titanium, etc.) with overlying portions of an aluminum based conductor pattern to convert the barrier contact into an intermetallic of aluminum with the transition metal. Although the method of this application enables the production of stable Schottky barrier diodes having a forward barrier height of about 0.67 ev. (electron volts), lower barrier heights are desired, as for example that of about 0.5 ev as initially exhibited by tantalum as a barrier contact with silicon. Unfortunately, the use of aluminum land patterns with barrier contacts of the transition metals, particularly tantalum, is very limited in view of rapid and easy reaction between aluminum and some transition metals during temperature excursions, such as normally encountered in integrated circuit fabrication processes. These reactions (e.g. between tantalum and aluminum) form intermetallic compounds (e.g. TaAl.sub.3) which shift the barrier heights to aluminum like values after high temperature excursions, e.g. from about 0.5 ev for tantalum as deposited on silicon to about 0.7 ev of aluminum after reaction. It would be desirable to retain stable low barrier height values as near as that exhibited by tantalum.